Post on 31-May-2020
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
58 | P a g e www.iiste.org
Determination of Some Quality and Safety Parameters for
Black Raisin Juice
Yakup Aslan (Corresponding author)
Department of Food Engineering, Faculty of Engineering, Siirt University
Postal Code: 56100, Siirt, Turkey
E-mail: dr_yakup@siirt.edu.tr
Hawsar S. Hussein
Department of Food Engineering, Faculty of Engineering, Siirt University
Postal Code: 56100, Siirt, Turkey
E-mail: hawsar9@gmail.com
Seerwan A. Abdullah
Department of Food Technology, University of Salahaddin
Postal Code: 44001, Arbil, Kurdistan, Iraq
E-mail: serwan.abdullah@su.edu.krd
Isa Cavidoglu
Department of Food Engineering, Faculty of Engineering, Van Yuzuncu Yil University
Postal Code: 65080, Van, Turkey
E-mail: isacavidoglu@yyu.edu.tr
The research is financed by Scientific Research Projects Coordinatorship (BAP) of Siirt University with code
2017-SİÜFEB-09
Abstract
The aim of the present study was to determine the safety and the quality parameters of raisin juice, such
as total soluble solids (TSS), pH, titratable acidity (TTA), kinds and quantity of sugars, phenolic acid
compounds, polyphenoloxidase (PPO) enzyme activity, water activity and total microbial counts. The
total soluble solids and pH values were significantly decreased after two weeks of storage, while the
titratable acidity in most samples were slightly changed. Glucose, fructose and sucrose as well as three
kinds of phenolic acids such as gallic, chlorogenic and vanilic acids were determined in all samples. Total
microbial contents of the freshly prepared raisin juice and of the raisin juice stored for one and two weeks
did not significantly changed. The water activity was slightly decreased, while the polyphenoloxidase
activity was significantly decreased, after storage for two weeks. Consequently, it can be said that the
freshly prepared raisin juice and the raisin juice stored for one week have superior sensorial properties
than the raisin juice stored for two weeks.
Keywords: Quality and safety, black raisin juice, phenolic acid compounds, polyphenoloxidase
1. Introduction
Grape is a non-climacteric fruiting that grows on the perennial and deciduous woody vines of the genus
Vitis that are mainly found in the moderate zones of the northern hemisphere and plurality divided
between America and Asia (Mullins et al., 1992).
Drying is one of the oldest methods used to preserve fruits by reducing moisture contents and reaction
rate to increase the shelf life of products. The moisture content is changed with drying period time of
samples in open sun drying. Initial moisture content in grape varied between 78% and 80% (w/w), was
reduced to the final water content of 22% (w/w). Three methods are used for dehydration of grapes; the
first one is a considered, sun or natural dryers, which it is low-cost process also the quality of natural
dried fruits is affected, and there is a little likeness to the fresh fruit. The second one is direct solar dryers.
In this dryer, the material to be dried is placed in poly net-shad-with or without transparent covers or side
panels. The third one is indirect solar dryer, which is the new and more effective technique of product
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
59 | P a g e www.iiste.org
drying. The drinking of fruit juices could have both positive and negative impact on the health of
consumers. Consumer demands safety and good processed foods with higher-quality properties have
encouraged better food production (Riahi and Ramaswamy, 2004). Freshly expressed grape juice consists
of 70 to 80% moisture and numerous dissolved solids. These soluble solids include many organic and
inorganic compounds.
Natural juice is the non-fermented or fermented product obtained from fruit through the physical methods
to maintain the basic structure and the quality. The juice can evoke the use of carbon dioxide (Iraqi
standard, 1988). Shi et al. (2003) were investigated universal phenolic acids in grapes contain benzoic
acids (galic acid, vanilinic acid, protocatechuic acid, and p-hydroxybenzoic acids) and cinnamic acids
(chlorogenic acid, caffeic acid coumaric acid, ferulic acid, and neochlorogenic acid). Phytochemicals
such as phenolic compounds, carotenoids, flavonoids, and vitamins in fruit juices play an important role
in disease protection (Gardner et al., 2000). The consumption of polyphenol-load juice improves
antioxidant status. (Bub et al., 2003).
Raisin juice consumed fresh fruits and especially is valuable for its tangy taste. It has a low shelf-life
during seven days storage in refrigerator; this is because of (1) natural contamination of raisin juice by
bacteria and molds, (2) enzymatic activities (Polyphenol oxidase and peroxidase) and these lead to
changes in taste and flavor during storage. Storage of raisin juices at refrigerator is not always best
method for the prevention of desirable quality of some fruits. Water used for juice preparation can be the
main source of microbial contamination. The polyphenol oxidase (PPO) enzyme is highly heat sensitive
and its activity reduced during the dehydration process. The residues of this enzyme interfere with the
discoloration of the raisins during storage. However, juice properties such as appearance, taste, and odor
are made undesirably changed via effects of enzymes such as PPO enzyme, peroxidase, and pectin
methylesterase (Awuah, 2007). For these case, there are big losses in their market value demandand
product quality (Gauillard and Richard-Forget 1997).
No such research has been carried out in this field, related to Arbil and Sulaymaniyah grapes, whichare
most widely used in Iraq. In order to develop awareness people about raisin juices, this studyefforts to
measure phenolic compounds, ascorbic acid, activity of polyphenol oxidase enzymeand total microbial
counts as the main parameters of quality and safety of raisin juice which ismechanically extracted.
The objectives of this study were: Characterizationof local black raisin (Vitis vinifera ) juice samples as
quality and safety parameters: (1) determination of some physical and chemical properties including pH,
brix values, and titratable acidity, (2) quantitative determination of phenolic acids using high-
performance liquid chromatography (HPLC) in flesh, seed and juice of local raisins. (3) quantitative
determination the activity of PPO in raisin and raisin juices,(4)microbial analysis during normal storage
of samples and (5) determination of sensory quality andthe acceptability of raisin juice drinks during
storage.
2. Experimentals
2.1. Materials
Hand-held Refractometer (RHB-50ATC/0-50% Brix) was purchased from Grandidex company (China
). Benchtop pH Meter BP3001 was purchased from Trans Instruments (S) Pte Ltd. (Jalan Kilang Barat,
Singapur). UltiMate 3000 HPLC systems and UV-Visible Evolution 200 were purchased from Thermo
Fisher Scientific (Waltham, MA USA). 4-Hydroxybenzoic acid, vanillic acids, and galic acids, D - (+)
glucose, acetoneitrile, methanol, phosphoric acid, formic acid, potassium phosphate monobasic, caffeic
acid, chlororogenic acids, sucrose, maltose monohydrate, D-fructose, ascorbic acid solution, polyphenol
oxidase enzyme solution, ethylenediaminetetraacetic acid (EDTA) solution, and potassium dihydrogen
phosphate were purchased from Sigma-Aldrich (Darmstadt, Germany). Phenolphthalein and sodium
hydroxide solution were purchased from Merck (Darmstadt, Germany). CHROMAFIL XTRA PVDF-
20/25 filter was purchased from Macherey-Nagel GmbH & Co. KG (Duren, Germany)
2.2. Methods
2.2.1. Collecting the black raisin samples
Locally black raisin juice made from seed Vitus vinifera grapes, four samples of black raisins (black
dried grapes) (Tre-rash varieties sample A, B) from Sulaimaniya and (Rashmiree samples C, D ) from
Arbil were collected from different local market. Two natural black raisin juice was extracted (A and C)
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
60 | P a g e www.iiste.org
and another two samples of raisin juice (B and D) were purchased from local market and then all samples
were used for experiments in order to investigate the quality and safety of locally raisin juices in four
bottles were stored at +4°C for two weeks.
2.2.2. Preparation of freshly squeezed raisin juice samples for analysis
The samples were prepared for analysis according to Abdullah's method (2012). 1 kg of raisins was
washed in tap water, and soaked in water for some hour, and mixed with 2.5 L of water and were grounded
before being squeezed with the cheese-cloth. The prepared raisin juice samples A and C were stored at
+4°C in the refrigerator for two weeks until used for analysis..
2.2.3. Determinatin of moisture content
5 g raisins from each sample (A to D) were dried in an oven at 70 °C for six hours, and then after cooling
in a desiccator, the samples were weighed to a constant value. Three replicates of weighing was
conducted for each sample. The Equation 1 was used to calculate the moisture content of samples
(Anonym, 1992).
n w d wM = W -W / W x 100 (1)
in where:
Mn = moisture content (%) of material
Ww = wet weight of the sample, and
Wd = weight of the sample after drying.
2.2.4. Determinatin of pH values of sample
The pH values of raisin juices were determined using pH meter (Benchtop pH Meter BP3001), at room
temperature. Before measurements, pH meter was calibrated using calibration buffers (pH 4, 7 and 10).
Raisin juices were tested three times (0, 7 and 14 days), in triplicate during storage in a refrigerator at +4 oC.
2.2.5. Determination of total soluble solids (Brix value)
Total soluble solid (TSS) contents of raisin juice samples were determined as Brix value using a
refractometer. To determine the Brix levels of the raisin juice samples, a few drops of the samples were
placed on the prism and closed before reading the refractometer scale, then the values at 20 °C were
recorded three times for each sample. TSS values of raisin juices were determined three times (0, 7 and
14 days) during storage in a refrigerator at +4 oC.
2.2.6. Determination of total titratable acidity
5 mL of raisin juices were taken for each sample and distilled water was added up to 100 ml in a 250 mL
conical flask, then titrated against 0.067 N sodium hydroxide solution using phenolphthalein as indicator.
Three replicates for each sample were conducted. The total titratable acidity (TTA) was calculated as g/L
tartaric acid according to Equation 2 (Xu et al., 2012) Raisin juices was tested three times (0, 7 and 14
days) during storage in a refrigerator at +4 oC.
NaOH (mL) x 0.1N NaOH x 0.075* x 1000TTA (g/L) Tartaric Acid =
Sample volume (mL) (2)
*= equivalent weight of tartaric acid
2.2.7. Determinations of kinds and quantity of sugar contents
Fructose, glucose, sucrose and maltose contents were determined using HPLC according to Turkish
Standard Method (TS, 2008). 7.5 ml of raisin juice and 2.5 ml of methanol were mixed in a flask and
shaked. After the mixture was filtered into HPLC vials using filters (pore size 0.25 μm) before HPLC
analysis. All samples were analyzed three times (0, 7 and 14 days) during storage at +4 oC.
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
61 | P a g e www.iiste.org
2.2.8. Determination of phenolic compounds by using HPLC
Determination of quality and quantity of phenolic acids in seeds and flesh of raisins individually as well
as in fresh raisin juice, after one week and two weeks from a squeezed raisin juice and stored at +4 °C in
the refrigerator until analysis have been done by using HPLC.
2.2.8.1. Sample preparation
A- Seed and flesh. 2 g grounded seed and flesh were taken into the volumetric flasks. 10 mL of distilled
water: methanol mixtures (95:5) were added and then were shaked in water bath at 200 rpm and 50 °C
for one hour, later were centrifuged at 5000 rpm for 5 min. The extracts were filtered into vials using
filters (pore sizes were 0.22 μm) and used for HPLC analysis.
B- Raisin juices. 0.5 mL methanol samples were added into volumetric flasks containing 9.5 ml juices
and after then this mixtures were filtered using vials with 0.22 μm filter. The filtrates were used for the
analysis with HPLC
Analytical column: Thermo 250mm x 4,6 mm x 5 um ID, hypersil gold
Flow rate: 0.75 mL / min
Solvent A: Water: Formic Acid (98: 2) Solvent B: water: Acetonitrile: Formic Acid (78:20:2)
Column temperature: 28 °C ± 1 °C
Injection volume: 20 μL
Standard stocks:
Gallic acid: 30 ppm (280 nm)
Colorogenic acid: 60 ppm (280 nm)
Caffeic acid: 20 ppm (320 nm)
4-Hydroxy aenzoic Acid: 40 ppm (280 nm)
Vanilic acid: 20 ppm (280 nm)
1 min 0.75 mL/min A %75 B %25.
5 min 0.75 mL/min A %50 B %50
10 min 0.75 mL/min A %25 B %75
12 min 0.75 mL/min A %25 B %75
15 min 0.75 mL/min A %0 B %100 (Slightly modified)
The system components were SPD-M20A diode array detector, SIL-20A HT autosampler, CTO-20A
column oven, and DGU-20A5 degas units. Chromatography was performed at wavelengths of 280 nm
and 320 nm (Table 1) and a C18 column with 250×4.6×5 mm dimensions was used. Mobile phase A;
water/formic acid (98:2), mobile phase B water/acetonitrile/formic acid (78:20:2) and the mobile phase
C was regulated as 100% methanol. Injection volume 20 μL, the flow rate was 0.75 mL/min and the
temperature was set at 28 oC. As the flow gradients of mobile phases were given above. As a flow
program External standards were used in order to the identification of the different phenolic compounds.
For example, phenolic acids standards were used at least with 5 different concentrations. All calibration
coefficients (R2) of standard plots were greater than 0.990.
Table 1. Analysis parameters of phenolic acids
Sample Name UV (nm) RT (min) 100% 80% 40% 20% 10%
Gallic acid 280 4.187 30 ppm 24 ppm 12 ppm 6 ppm 3 ppm
Cholorogenic acid 280 4.877 60 ppm 48 ppm 24 ppm 12 ppm 6 ppm
Caffeic acid 320 6.797 20 ppm 16 ppm 8 ppm 4 ppm 2 ppm
4-hydroxy benzoic acid 280 6.763 40 ppm 32 ppm 16 ppm 8 ppm 4 ppm
Vanilic Acid 280 9.793 20 ppm 16 ppm 8 ppm 4 ppm 2 ppm
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
62 | P a g e www.iiste.org
2.2.9. Enzymatic assay of Poly Phenol Oxidase
Method: Continuous Spectrophotometric activity determination.
Reagents:
1. 50 mM potassium phosphate buffer, pH 6.5
2. 5 mM L-3,4-Dihydroxyphenylalanine solution.
3. 2.1 mM L-ascorbic acid solution.
4. 0.065 mM Ethylenediaminetetraacetic acid solution (EDTA).
5. Poly Phenol Oxidase (PPO) enzyme solution (containing 500 - 1000 units/mL of PPO in cold reagent
A.)
Procedure: The following reagents were pipetted (in milliliters) into suitable quartz cuvettes (Table 2).
They were mixed by inversion and equilibrate to 25°C. Monitor the A265 nm until constant, using a
suitable thermostatted spectrophotometer. Then added reagent E. They immediately mixed by inversion
and record the decrease in A265 nm for approximately 5 minutes.
The A265 nm/minute is obtained using the maximum linear rate for both the test and blank.
Calculation: Enzyme unit was calculated using Equation 3.
265 nm 265 nmΔA /min Test - ΔA / min Blank
(0.00Units
1) (m / mg enzyme
g Enzyme /=
RM) (3)
0.001 = the change in A265 nm/minute per unit PPO at pH 6.5 at 25 °C in a 3 mL reaction mixture.
RM = Reaction Mixture (3 mL)
Unit definition: One unit was enzyme amount that caused the change in A265 nm of 0.001 per minute in a
3 mL reaction mix containing L-3,4-dihydroxyphenylalanine and L-ascorbic acid at pH 6.5 at 25°C.
Final assay concentrations: In 3 mL reaction mixture, the final concentrations: potassium phosphate
buffer was 50 mM, L-ascorbic acide was 0.17 mM and PPO was 50-100 units (Dawson et al., 1955;
Marumo et al., 1986).
2.2.10. Water activity
Measurement of water activity (aw) was carried out using a water activity meter at 25°C. The raisin
samples were first sliced into thin pieces and placed in a small chamber and a few drops of the raisin
juices were added into the reading cell. All samples were tested 3 times (fresh, after one week and two
weeks) during storage in a refrigerator at +4 oC. The water in the chamber air was measured after reaching
equilibrium conditions and the result at 25°C were recorded for each samples (steady state) (Aktas and
Polat, 2007).
2.2.11. Total bacterial counts
Total bacterial counts were determined on 0, 7 and 14. days of storage in a refrigerator at +4°C. 10 mL
of the samples were diluted with 90 mL of sterile distilled water and mixed well to obtain 10-1 dilution.
Serial dilutions 8-10 were prepared and spread plate technique was used on appropriate selective
Table 2. The amounts of reagents and blank
Reagent Test Blank
Reagent A (Buffer ) 2.60 2.80
Reagent B (L-DOPA) 0.10 0.10
Reagent C (Ascorbic Acid) 0.10 0.00
Reagent D (EDTA) 0.10 0.10
Reagent E (Enzyme solution ) 0.10 0.00
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
63 | P a g e www.iiste.org
media. Duplicate nutrient agar plates were used for each sample and incubated at 37±1°C for 48 hours.
Plates containing 30-300 CFU/mL were selected for counting 3 times during storage in a refrigerator at
+4°C (Braide et al., 2012).
Number of colonies on plate x Reciprocal of dilution of samples = Number of bacteria/mL
2.2.11. Sensorial evaluation
Sensorial evaluation of raisin juice is very important and gives a reliable opinion to appear the
acceptability of new products. Samples were presented to at least ten panelists inside a plastic bottle.
Appearance, aroma, taste, sweetness, and texture/mouth-feel were evaluated by the panelists on 0, 7, and
14 days of storage in terms of consumer acceptability. Panelists scored the samples using a five-point
hedonic scale where a score of 1 dislike a lot and a score of 5 like a lot (Watts, 1989).
2.2.12. Statistical analysis
The PROC GLM (General Linear Model) procedure (SAS, 1999) was used to analyze the data in this
study. Moreover, the Duncan multiple range tests used to a comparison between means for all traits
under ( ≥ 0.05) level.
3. Results and Discussions
3.1. Determination of moisture content in raisins
Determining the moisture content of raisin plays an important role in estimating the shelf life
consumables of grape berries. The grape properties directly affect raisin quality. Raisin is not considered
as the agricultural perishable products which can be hardly deteriorated by microorganism because of its
low content of moisture and water (Christensen, 1995). The obtained data showed that the highest
moisture content (16.5%) determined in sample B whereas sample C showed the lowest moisture content
(14.9%) (Fig. 1). Moreover, no significant differences observed between moisture content in all samples,
except sample C which was significantly different from other samples. This is compatible with who
reported the range of moisture content from 11-18% (Christensen, 1995).
3.2. Determination of pH values
One of the crucial quality properties that illuminate the stability of bioactive compounds in fruit juice is
pH. Compounds such as organic acids are responsible for providing low pH in fruit juice. The pH can
either rise or fall. (Tasnim et al. 2010). Fig. 2 showed that, fresh raisin juice sample A had the highest
value of pH (4.23) and sample D had lowest value pH (2.96) in raisin juice sample refrigerated at the
end of period (14 days), as well as the maximum differences between the fresh sample and last day of
refrigerated sample was (-1.10 ) in sample D. At the same time, the influence of storage time had dramatic
effects on the pH value in all samples; there was a significant decrease in pH value after 1 and 2 weeks.
Boulton (1980) reported that the precipitation of potassium bitartrate either during fermentation or
stabilization will cause fall of pH. This result agrees with the results obtained in study of Mehmood et al
(2008) related to the study of the effect of pasteurization and chemical preservatives on the quality and
shelf stability of apple juice stored at ambient temperature for three months. However, similar results
were found by Wisal et al (2013). The reason of decrease in the pH value during storage, it is possible to
have biochemical reaction taking place during storage periods together with microbial action in the juices
(Ibrahim, 2016). Otherwise, these results are a reverse portion of the results obtained by Mgaya-Kilima
et al (2014), and Islam et al (2015).
3.3. Determination of TSS
TSS values of raisin juice stored under different storage period were given in Fig. 3. The total soluble
solid values were ranged from 18.06% to 20.33% in fresh raisin juice A and B, respectively. However,
the maximum value reduction of TSS was reached, while the lowest reduction was reached in samples
after two weeks of storage. Moreover, in refrigeration condition, the TSS in all samples was decreased
significantly after 2 weeks, but there was no significant difference between most of the samples after 1
week. This finding is consistent with the study of Wisal, et al (2013). They reported that approximately
0.5 Brix of TSS decreased in strawberry juice after being refrigerated for 20 days. Arin and Akdemir
(2004) found the same results. TSS decrease at the end of the storage period (2 months). Bull et al. (2004)
also investigated that the TSS by Brix of thermally processed Valencia and Navel orange juice.
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
64 | P a g e www.iiste.org
Fig 1. Moisture contents of raisin samples (A-D)
Fig 2. pH values of raisin juices (Samples A-D)
Fig 3. Total Soluble Solids (°Brix) of raisin juices
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
65 | P a g e www.iiste.org
TSS was not significantly changed during storage time in a refrigerator at +4 °C. On the other hand, this
is a contrast with the observation by Mgaya-Kilima (2014) and Bhardwaj and Pandey (2011). Retention
or a slight increase in the TSS of the roselle-fruit blends observed during 6 months at both storage
temperatures +4 °C and 28 °C. Increase in total soluble solids may be due to break down of
polysaccharides into monosaccharide and oligosaccharides that decreased possibly due to fermentation
of these sugars into ethyl alcohol, carbon dioxide, and water.
3.4. Determination of TTA
Tartaric acid is most important acidic component in grape or raisin juice, and important standard for
grape juice (Kanellis and Roubelakis, 1993). The main organic acid extracts in grapes are tartaric, malic,
also little quantity of citric and succinic acid (Kliewer, 1966).The other acids in raisins obtained from
different grape varieties return to tartaric, malic, citric, succinic acids during storage. Statistical analysis
showed that the storage does not influence the titratable acidity in most samples. The formation of lactic
acid, either during the alcoholic fermentation or the malo-lactic fermentation leads to lowering of both
the total acidity and the titratable acidity (Boulton 1980). The same author reported that the precipitation
of potassium bitartrate either during fermentation or stabilization will reduce both the total acidity and
titratable acidity. As shown in Fig. 4, there are a significant difference between most of the fresh samples.
The TTA in fresh samples B and D, were determined to be 3.01 g/L and 8.14 g/L, respectively. The
difference in TTA between the grape cultivars was expected, this can be due to some factors such as
climate, variety, genetic and cultural practice (Dharmadhikari, 2010). High TTA can be an indication of
the presence of tartaric acid (Kodur, 2011). As seen in the figure, D sample stored for two weeks showed
the most TTA value (9.57 g/L) while fresh B sample had showed the lowest TTA value (3.01 g/L).
According to Fig. 5, the TTA values of all samples had increased linearly with decreasing pH values.
3.5. Qualitative and quantitative determinations of sugar contents
One of the most crucial components of fruit products, essential for and also act as a natural food for
prolonging of shelf life are sugars (Bhardwaj and Pandey 2011). The sugar content in grape is essential
to produce raisins or table grape with an acceptable quality. It has been stated that the initial sugar content
before drying should be more than 22° Brix (Amerine, 1981). The raisin juice has a sweet taste;
consequently, the major parameters for evaluating the quality of raisin juice are the concentration of
sugars and pH acidity. Basically, with trace content of sucrose, glucose, and fructose which are present
in grape or raisin juice, as well as there were considered the most soluble in water because there are
belonged to reducing sugar as a monosaccharide. More significantly the hexose sugars in raisin juice are
converted into alcohol through anaerobic fermentation conducted by yeasts.
Fig 4. TTA of raisin juices
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
66 | P a g e www.iiste.org
Fig 5. Relationship between pH and TTA.
In the present study, HPLC method was used to determine the quality and quantity profiles and
concentrations of sugars in samples are shown in Table 3. Identified three types of sugars in raisin juice
which are included glucose (53.52 - 99.127 g/L) and fructose (45.04 -104.80 g/L) as well as the trace
amount of sucrose (0-16.67 g/L). These results were consistent with the results of Duran (2014) who
observed that glucose and fructose concentration of 8 different grape cultivars were the predominant
sugars in grape berries ranging from 89.4 to 144.24 g/L and from 92.1 to 139.4 g/L, respectively.
According to the table, glucose/fructose ratio was between 0.97-1.07. Furthermore, the ratio of
glucose/(fructose+ sucrose) was between 0.95-1.06. These are similar to results reported by several
researchers. Shiraishi et al.(2010) reported that the ratio of glucose/(fructose + sucrose) is higher than
0.8 depend on types of grapes based on sugar composition. Dai et al (2011) reported that the ratio of
glucose to fructose ranged between 0.47-1.12, depend on the maturity of grapes. On the other hand,
Elsheikh, et al (2014), illustrated that, the total sugars of Abu Samaka concentrate stored in the
refrigerator decreased after 2 months, these illustrate consistent with the obtained results in the present
study.
3.6. Determination of phenolic compounds by using HPLC
Refrigeration slows down the chemical and biological processes in foods, and the accompanying
deterioration and loss of quality of nutrients. The occurrence of sufficient amount of phytochemical such
as carotenoids, flavonoids, and bioactivity of phenolic acid compounds in grape or raisin juice can be
standard the quality and high nutrition value. Kahkonen et al., (2012) described that, the grape juice is a
major source of bioactive compounds such as phenolic compounds and the consumption of this product
is related to several health benefits to consumers. Table 4 summarizes all identification and quantification
of phenolic compounds determined in studied raisins (seed and flesh), fresh raisin juice samples and
raisin juice refrigerated for 14 days.
In this study, the result showed that chlorogenic acid, gallic, and vanilic acid were detected as a three
types of phenolic bioactive compounds in both seeds and flesh of raisins individually. Furthermore, the
sum of total phenolic acids quantified in seeds and flesh of raisins varied from 933.57 to 1434.13 mg/ kg
and 1060.85 to 2645.59 mg/kg for samples B, D, A and C, respectively.
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
67 | P a g e www.iiste.org
Table 3. Sugar content of black raisin juices
Sugar Concentrations (g/L) Significant Ratios (%)
Samples Times Glucose Fructose Sucrose Glu/Fru Glu/(Fru+ Suc)
A Fresh 79.30 83.43 0 0.95 0.95
A One week 77.69 82.85 0.26 0.93 0.93
A Two weeks 53.52 45.04 0.89 1.18 1.16
B Fresh 99.12 104.80 6.52 0.94 0.89
B One week 94.39 100.51 0.01 0.93 0.93
B Two weeks 99.10 98.71 0.46 1.00 0.99
C Fresh 63.15 57.90 0 1.09 1.09
C One week 62.86 60.05 0.36 1.04 1.04
C Two weeks 60.05 53.26 0.04 1.12 1.12
D Fresh 67.37 68.85 16.67 0.97 0.78
D One week 66.60 70.64 0.16 0.94 0.94
D Two weeks 56.93 53.15 0.15 1.07 1.06
Table 4. Phenolic acids in seed and flesh of raisin
Phenolic Acid Concentrations (mg/kg)
A B C D
Phenolic acids Seed Flesh Seed Flesh Seed Flesh Seed Flesh
Gallic acid 404.96 532.69 607.78 650.46 699.31 704.01 818.76 745.68
Chlorogenic acid 604.86 428.26 278.09 843.84 592.5 1855.8 599.7 1137.34
Vanilic acid 27.19 99.90 47.70 108.55 15.75 85.78 15.67 77.22
Total 1037.01 1060.85 933.57 1602.85 1307.56 2645.59 1434.13 1960.24
The variation of phenolic concentration in seeds and flesh of raisin is caused from the variety of grapes,
drying process to produce raisins and storage period, as described by Hassan et al (2015). The results we
obtained in this study are in good agreement with the results obtained by Shi et al (2003) and by Eyduran
et al (2015). On the other hand, the results given in Table 5 shows that the same phenolic acid compounds
identified with a different concentration in fresh raisin juice and in refrigerated raisin juices for one and
two weeks. In terms of gallic, chlorogenic and vanilic acids the highest contents were proved with fresh
raisin juice samples D, C and A respectively, which were significantly different from the others. This
result is indicated the high nutrient value regarding of bioavailability of phenolic compounds. The
increase and reduce levels of this compounds as well as create and degrade the organoleptic qualities of
raisin juice for each term of phenolic compounds individually, after one and two weeks of storage were
observed. The gallic acid compound was significantly increased in sample A after one week and at the
end of storage period of raisin juice, while slightly increased in sample C after both storages as well as
sample D was slightly increased after one week and significantly increased after two weeks of storage
for the same term of phenolic acids compound (Fig. 6). Hence, the reduce of gallic acid in fresh raisin
juice sample B was no significantly difference between one and two weeks of storage. However, the
highest increase in the level (17.23) of gallic acid was recorded in sample A after two weeks. In the
present study, clorogenic acid was significantly increased in sample A and B after one week storage,
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
68 | P a g e www.iiste.org
while the vanilic acid compound was significantly changed in samples A and did not significantly
changed in sample B after one and two weeks. At the end of refrigerated
Table 5. Galic, chlorogenic and vanilic acids in raisin juices
Phenolic Acid Concentrations (mg/kg)
Phenolic acids A B C D Storage
Galic acids 67.99 ± 0.53 52.09 ± 0.10 104.37 ±0.15 115.63 ± 0.56
Fresh Chlorogenic acid 67.96 ± 0.67 29.48 ± 0.44 242.87± 0.85 132.66 ± 0.20
Vanilic acid 17.67 ± 0.42 6.61 ± 0.01 13.68 ± 0. 65 8.43 ± 0.02
Total 153.62 88.18 360.91 256.71
Galic acids 81.38 ± 0.09 50.86 ± 0.74 106.07 ± 0.37 118.28 ± 0.47
One week Chlorogenic acid 84.28 ± 0.23 33.66 ± 0.29 232.98 ± 0.05 70.37 ± 1.65
Vanilic acid 12.72 ± 0.02 6.68 ± 0.10 12.7 5± 0.15 7.95 ± 0.17
Total 178.38 91.19 351.80 196.60
Galic acids 85.22 ± 0.28 47.48 ± 0.81 110.03 ± 0.20 126.03 ± 0.09
Two weeks Chlorogenic acid 79.30 ± 0.37 26.99 ± 028 232.49 ± 0.01 42.62 ± 0.18
Vanilic acid 12.99 ± 0.05 6.32 ± 0.02 13.34 ± 0.35 8.31 ± 0.27
Total 177.51 80.79 355.86 176.96
Fig 6. Phenolic acids in raisin juice.
storage period, the variations in the availability of phenolic compounds might be referring to the
fermentation and some chemical reaction and enzyme activity as well as the type of grapes used for
production of raisins and juices may greatly influence its phenolic composition (Eyduran, et al 2015).
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
69 | P a g e www.iiste.org
3.7. Assay of PPO activity
One of the main obstacles of undesired of quality of fruit juice results from enzymatic browning, which
is caused by the act of polyphenol oxidase enzyme. The freshness of fruit juices can be prolonged for a
few days by storing in a refrigerator. Thus, the microbial contamination that reduce the quality, distording
the sensorial evaluation and causes turbidity, browning and sedimenting during storage can be prevented
(Lea, 1994). Yemenicioğlu and Cemeroglu (1997) had illustrated that the oxidative enzymes such as
polyphenol oxidase and peroxidase are the main factor in reducing the nutritional and sensorial values as
well as color and flavor of fresh fruit juice. As shown in Fig. 7, the highest value of polyphenoloxidase
enzyme was observed in raw raisin sample D, and it was superior to other samples. The lowest level of
PPO was found in sample A. Furthermore, under the current experimental conditions, among fresh raisin
juice samples, the maximum value of PPO was found in fresh raisin juice sample A and the minimum
value was observed in sample D (Fig. 8). Perhaps the variation in the results is due to the species of the
grapes, the acidity, the storage time, the type of drying and juice treatment process. These results are
consistent with results obtained in previous studies (Wesche-Ebeling and Montgomery, 1990; Zemel et
al., 1990).
3.8. Water activity
Water activity (aw) indicates how tightly water is bound, structurally or chemically, in food products. he
predicts food safety and stability with respect to microbial growth, chemical/biochemical reaction rates,
and physical properties are combined the concept of aw which has been an essential role for food safety.
To attempt to preserve the quality and safety or the chemical stability (Non- enzymatic browning
reaction) of foods and activation of microorganisms, it’s possible by controlling the water activity content
in food products. Therefore, the non-enzymatic browning reaction increases with increasing as well as
this reaction will reach to the maximum reaction when the range of reaching 0.6 to 0.7. The lowest aw at
which the vast majority of food spoilage bacteria will grow is about 0.90. The aw of molds
Fig 7. PPO activities in raisins
A B C D
Seri 1 40 118 48 152
c
b
c
a
0
20
40
60
80
100
120
140
160
180
PP
O A
ctiv
itiy
(E
U/m
L)
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
70 | P a g e www.iiste.org
Fig 8. PPO activities in raisin juices
and yeasts growth are about 0.61 with the lower limit for growth of mycotoxigenic molds at 0.78 aw
(Beuchat 1981). The aw of pure water is 1.00 and the aw of a completely dehydrated food is 0.00. The aw
of a food on this scale from 0.00 - 1.00 is related to the equilibrium relative humidity of the food on a
scale of 0-100%. Thus, % Equilibrium Relative Humidity (ERH) = aw x 100. The aw of a food describes
the degree to which water is "bound" in the food, its availability to participate in chemical/biochemical
reactions, and its availability to facilitate the growth of microorganisms (Mossel and others 1995). The
results for the characterization of the raisins and fresh raisin juices as well as raisin juices refrigerated
for two weeks are represented in Fig. 9 and Fig. 10, respectively. The contribution to the of raisins and
fresh raisins ranged from 0.484-0.519 and 0.949-0.955, respectively in 25˚C. The results of aw in raisins
were lower than those found by Mossel et al. (1996), the approximate aw levels in dried fruits between
0.55-0.80. The difference might be due to the drying process, and juice processing. Furthermore, the aw
of the most of raisin juice products slightly increases with increasing the shelf life of product for one
week and at the end of refrigerated storage period. This phenomenon is due to decease of total soluble
solid.
Fig 9. Water activities in raisins
b
a
b
a
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
71 | P a g e www.iiste.org
Fig 10. Water activities in raisin juice.
3.9. Total bacterial counts
Ensuring food safety, adequate nutrition content and bioavailability free from preservatives and additives
are the curiosities of public health and consumer protection, which have been processed in a fashion to
minimize the influence on the original food products (Reed and Grivetti, 2000). Enhancing consumer's
health due to inhibition of diseases, it is important the performance of hygienic condition during raisin
juice production. Good manufacturing practice (GMP) has influenced the quality and safety of raisin
juice. Raisin juice will be contaminated at any points from raw material to end of the production and
could be the source of infectious pathogens till to reach the consumers. The microbial population depends
on several factors such as pH, aw true hygienic condition, treatments, and storage condition. The
refrigerator is not always the best way to extend the shelf life with retention of the nutrient value of fruit
juice.
It can be seen in the histogram that the increase in the number of micro-organisms was during the first
week of refrigeration in most samples, then it accelerated at the end of storage period, as well as the
results showed the maximum and minimum initial of total count microorganisms in fresh raisin juice
were 8.48 and 7.09 CFU/ml, in samples D and B, respectively (Fig. 11). The reason for this result might
be due to the degree of achieving hygienic condition during raisin juice processing. Furthermore, there
were no significant difference in the population of microorganisms in all fresh samples compares the
samples at the middle and the end of storage period in refrigerator or the survival of microorganisms in
fresh raisin juice was slightly increased after one and two weeks of storage in refrigerator and these
results are in accordance with a previous study done by Elsheikh et al (2014) that investigated the total
viable count was nil at zero time of storage and started to increase after 2 months. On teh other hand, this
results agrees with results obtained by Kaddumukasa (2017) in the microbiological analyses of passion
fruit, pineapple, and mango juices in dark and light bottles at 24°C and 4°C were conducted in Kampala,
Uganda for 12 days for juices.
3.10. Sensorial evaluation
In this study, sensorial evaluation is used as an essential part of quality control as well as quality assurance
of fresh raisin juice and samples refrigerated for two weeks. Sensory analysis was performed with 10
panelists (5 females and 5 males and between 18 and 40 years of age), on first week, second week and
third week of storage in terms of consumer acceptability. The evaluated attributes were the intensity of
sensory properties was included (appearance, aroma, taste, sweetness and texture mouth feel). Panelists
scored the samples using a five-point hedonic scale where a score of 1 extremely dislike and a score of
5 extremely like.
Table 6 shows that the fresh raisin juice samples showed the highest acceptability in all the sensory
attributes. This may be related to the freshness of the juice (Akusu, et al., 2016). Further, there was
significantly decrease in all sensory characteristics of fresh raisin juice compared to other samples at the
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
72 | P a g e www.iiste.org
end of storage period under the refrigerated condition, as illustrated in Table 6. This result opposite the
work of Adebayo Tayo and Akpeji (2016), who reported that there was no significant difference in taste,
aroma, color, and appearance of the probioticated juice samples during 4 weeks storage.
Otherwise, the appearance evaluation of the fresh raisin juice for all samples compared with the samples
stored for 1 week exhibited similar trends as well as significantly decrease of flavor, taste and sweetness
characteristics in all fresh raisin juice samples compared their counterparts stored for 1 week, except
samples B and A. This result agree with study of Akusu et al (2016) who found that sensory evaluation
result showed a significant difference in the attributes of colour, flavour, taste and overall acceptability
of the orange/pineapple juice blends compared to the reference sample.
Although, the results showed that the texture mouth feel in samples A and C was changed significantly
after 1 week, in contrast, a comparison results of the texture mouthfeel of fresh raisin juice in samples
B and D to the first storage study were no significant. Furthermore, these results showed significant
differences between all fresh raisin juice samples and refrigerated for 14 days, except sample A. Similar
results reported by Bhardwaj and Nandal (2014). Their results indicated that flavour, colour and bitterness
score of juice blends, decreased with advancement of storage period.
The reasons for the changed the sensory evaluation, might be referring to some chemical, microbial, and
enzymatic reactions as described by same authers and the juice blend can be kept conveniently for three
weeks without preservatives, in contrast to the results reported by Islam et al (2015).
Fig 11. Total bacterial counts
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
73 | P a g e www.iiste.org
Table 6. Sensorial evaluation of raisin juices
Test Time Color Flavor Taste Sweetness Texture / Mouthfeel
A Fresh 4 ± 0.62ab 4.35± 0.52a 3.75± 0.67a 3.40± 0.80 a 3.75± 1.06 a
B Fresh 3.60 ± 0.73abc 3.75 ±0.67abc 3.40± 3.93a 3.05 ± 1.25a 3.30± 0.67ab
C Fresh 3.80 ± 0.88ab 3.80± 1.22ab 3.75± 0.35a 3.35 ± 0.81a 3.80 ± 0.97a
D Fresh 4.25 ± 0.75a 3.85± 1.10ab 3.65± 0.78a 3.50 ± 0.91a 3.20± 1.25ab
A One week 3.35± 0.78bcd 2.60± 0.73de 2.35± 0.85b 1.95 ± 0.76cd 2.5± 1.08b
B One week 3.85± 0.62ab 3.10± 1.24bcd 3.25± 0.97a 2.90± 0.80ab 2.75± 1.07b
C Oneweek 3.55± 0.59abc 2.35± 0.57def 2 ± 0.33bc 2 ±0.62cd 2.50± 0.81b
D One week 4.05 ±0.49ab 3± 0.52cd 2.20± 0.71b 2.30± 0.91bc 2.50± 0.57b
A Two weeks 3.1 ± 0.61cd 1.5± 0.52gh 1.30± 0.34ed 1.35 ±0.52de 1.25± 0.58c
B Two weeks 2.80±0.53d 1.80± 0.67fhg 1.25± 0.63ed 1.15± 0.78 e 1.55± 0.55 c
C Two weeks 2.70± .58 d 1.25± 0.58 h 0.70± 0.53 e 1.10± 0.51 e 1.35± 0.57 c
D Two weeks 3.90± 0.80 ab 2.20± 0.75efg 1.50 ± 0.47 cd 1.40± 0.56 ed 1.50± 0.57 c
4. Conclusions
In this study, the differences in terms of both quality and safety of the samples were given. As a result it
can be said that the fresh raisin juice samples were superior than the stored samples in refrigerator during
1-2 weeks based on quality parameters such as total soluble solids, pH, the quantity of phenolic acids,
sensory evaluation, appearance, sweetness and aroma.
Furthermore, in this research three types of sugars which include glucose, fructose, and sucrose as well
as three types of essential bioactive phenolic acid compounds which involves gallic, chlorogenic and
vanilic acids with different concentrations have been identified.
Consequently, it can be said the variation of phenolic concentration in seeds and flesh of raisin is caused
from the variety of grapes, drying process to produce raisins and storage period. Furthermore, the
evaluation of bacterial count and water activity showed that the safety of untreated raisin juice samples
depends on the good hygienic practices (GMP) and storage condition until to reach the consumers.
Acknowledgement
The authors acknowledge to Scientific Research Projects Coordinatorship of Siirt University for their
financial support.
References
Abdullah, S.A. (2012). Alternative processing techniques for pasteurization of liquid
foods:Microwave, ohmic heating and ultraviolet light, Doctoral dissertation, University of
Hawai'i at Manoa, Manoa 1-143.
Adebayo, Tayo, B., Akpeji, S. 2016. Probiotic viability, physicochemical and sensory properties of
probiotic pineapple juice. Ferment. 2(4): 20-31.
Aktas, T., Polat, R. (2007). Changes in the drying characteristics and water activity values of selected
pistachio cultivars during hot air drying. J. Food Process. Eng. 30(5): 607-624.
Akusu, O.M., Kiin-Kabari, D.B., Ebere, C.O. (2016). Quality characteristics of orange/pineapple fruit
juice blends. Am. J. Food Sci. Technol. 4(2): 43-47.
Amerine, M.A., Ough, C.S. (1981). Methods for Analysis of Musts and Wines. J. Inst. Brew. 87(4):
223-224.
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
74 | P a g e www.iiste.org
Arin, S., Akdemir, S. (2004). Quality properties changing of grape during storage period. J.
Biol.Sci. 4(2): 253-257.
Awuah, G.B., Ramaswamy, H.S., Economides, A. (2007). Thermal processing and quality: principles
and overview. Chem. Eng. Process. 46(6): 584-602.
Beuchat, L.R. (1981). Microbial stability as affected by water activity. Cereal Foods World. 26(7):
345-349.
Bhardwaj, R.L., Nandal, U., (2014). Effect of storage temperature on physico-chemical and sensory
evaluation of kinnow mandarin juice blends. J. Food Process. Technol. 5(8):1-4.
Bhardwaj, R.L., Pandey, S. (2011). Juice blends—a way of utilization of under-utilized fruits,
vegetables, and spices: a review. Crit. Rev. in Food Sci. Nutr. 51(6): 563-570.
Boulton, R. (1980). The general relationship between potassium, sodium and pH in grape juice and
wine. Am. J. Enol. Vitic. 31(2): 182-186.
Braide, W., Oranusi, S.U., Otali, C.C. (2012). Microbiological status of processed fruit juice sold in
the commercial city of Onitsha. Scholarly J. Biol. Sci. 1(3): 25-30.
Bub, A., Watzl, B., Blockhaus, M., Briviba, K., Liegibel, U., Müller, H., Pool-Zobel, B.L.,
Rechkemmer, G. (2003). Fruit juice consumption modulates antioxidative status, immune
status and DNA damage. J. Nutr. Biochem. 14(2): 90-98.
Bull, M.K., Zerdin, K., Howe, E., Goicoechea, D., Paramanandhan, P., Stockman, R., Sellahewa, J.,
Szabo, E.A., Johnson, R.L., Stewart, C.M. (2004). The effect of high pressure processing on
the microbial, physical and chemical properties of Valencia and Navel orange juice. Innov.
Food Sci. Emerg. Technol. 5: 135-149.
Chitarra, M.I.F., Chitarra, A.B. (2005). Post-Harvest Fruits and Vegetables: Physiology and
Handling. 2nd ed., UFLA: Lavras, Brazil, p. 785.
Christensen, L.P., Bianchi, M.L., Lynn, C.D., Kasimatis, A.N., Miller, M.W. (1995). The effects of
harvest date on Thompson seedless grapes and raisins. I. Fruit composition, characteristics, and
yield. Am. J. Enol. Vitic. 46(1): 10-16.
Dai, Z.W., Ollat, N., Gomès, E., Decroocq, S., Tandonnet, J.P., Bordenave, L., Pieri, P., Hilbert, G.,
Kappel, C., van Leeuwen, C., Vivin, P. (2011). Ecophysiological, genetic, and molecular
causes of variation in grape berry weight and composition: a review. Am. J. Enol. Vitic. 62(4):
413-425.
Dawson, C.R., and Magee, R.J. (1955). Plant tyrosinase (polyphenol oxidase). Methods Enzymol.2:
817-821.
Dharmadhikari, M. (2010). Composition of grapes. Iowa StateUniversity, Iowa State University
Extension: Ames,
Iowa. (https://www.extension.iastate.edu/wine/files/page/files/compositionofgrapes.pdf)
(February 12, 2019)
Duran, Z. (2014). Malatya ve Elaziğ illerinde yetiştirilen bazi üzüm çeşitlerinin organik asit, şeker ve
fenolik madde bileşikleri ile antioksidan aktivitelerinin belirlenmesi. M.Sc. Thesis, İnönü
University, 1-62.
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
75 | P a g e www.iiste.org
Elsheikh, A.O., Nour, A.E.A., Elkhalifa, A.E.O. (2014). Effect of storage on the quality attributes of
concentrates of two mango (Mangifera indica) varieties grown in Sudan. Br. J. Appl. Sci.
Technol. 4(14): 2069-2078.
Eyduran, S.P., Akin, M., Ercisli, S., Eyduran, E., Maghradze, D. (2015). Sugars, organic acids,
and phenolic compounds of ancient grape cultivars (Vitis vinifera L.) from Igdir province of Eastern
Turkey. Biol. Res. 48(2): 2-8.
Gardner, P.T., White, T.A., McPhail, D.B., Duthie, G.G. (2000). The relative contributions of vitamin
C, carotenoids and phenolics to the antioxidant potential of fruit juices. Food Chem. 68(4): 471-
474.
Gauillard, F., Richard-Forget, F. (1997). Polyphenoloxidases from Williams pear (Pyrus communis
L, cv Williams): activation, purification and some properties. J. Sci. Food Agric. 74(1), 49-56.
Hassan, N.A., El-Halwagi, A.A., Sayed, H.A. (2012). Photochemical, antioxidant and chemical
properties accession growth in Egypt. World Appl. Sci. J. 16(8): 1065-1073.
Ibrahim, M.A. (2016). Effect of different storage condition on pH and vitamin C content in some
selected fruit juices (pineapple, pawpaw and watermelon). Int. J. Biochem. Res. Rev. 2: 1-5.
Iraqi standard. (1988). Grape juices preserved exclusively by physical means. 1207, pp 1.
Kaddumukasa, P.P., Imathiu, S.M., Mathara, J.M., Nakavuma, J.L. (2017). Influence of
physicochemical parameters on storage stability: Microbiological quality of fresh unpasteurized
fruit juices. Food Sci. Nutr. 5(6): 1098-1105.
Kahkönen, M., Kylli, P., Ollilainen, V., Salminen, J.P. and Heinonen, M. (2012). Antioxidant activity
of isolated ellagitannins from red raspberries and cloudberries. J. Agric. Food Chem. 60(5): 1167-
1174.
Kanellis, A.K. and Roubelakis-Angelakis, K.A. (1993). Grape. In: Seymour, G.B., Taylor J.E.,
Tucker G.A. (Eds.). Biochemistry of fruit ripening. Chapman and Hall, London, 189-234.
Kliewer, W.M. (1966). Sugars and organic acids of Vitis vinifera. Plant physiol. 41(6): 923-931.
Lea A.G.H. (1994). Apple juice. In: J. Fry, G. G. Martin, M. Lees (auth.), P. R. Ashurst (Eds.).
Production and Packaging of Non-Carbonated Fruit Juices and Fruit Beverages. Chapman & Hall.
Glasgow. 153-196
Marumo, K., Waite, J.H. (1986). Optimization of hydroxylation of tyrosine and tyrosine-containing
peptides by mushroom tyrosinase. Biochim. Biophys. Acta. 872 (1-2): 98-103.
Mehmood, Z., Zeb, A., Ayub, M., Bibi, N., Badshah, A., Ihsanullah, I. (2008). Effect of
pasteurization and chemical preservatives on the quality and shelf stability of apple juice. Am.
J. Food Sci. Technol. 3(2): 147-153.
Mgaya-Kilima B., Remberg, S.F., Chove, B.E., Wicklun T. (2014). Influence of storage temperature
and time on the physicochemical and bioactive properties of Roselle-fruit juice blends in
plastic bottle. Food Sci. Nutr. 2(2): 181–191.
Mossel, D.A.A., Corry, J.E., Struijk, C.B., Baird, R.M. (1996). Essentials of the microbiology of
foods: a textbook for advanced studies. John Wiley & Sons. New Jersey, 1-736
Mullins, M.G., Bouquet, A., Williams, L.E. (1992). Biology of the grapevine. Cambridge University
Press. Cambridge, 17-36.
International Journal of Scientific and Technological Research www.iiste.org ISSN 2422-8702 (Online), DOI: 10.7176/JSTR/5-4-08 Vol.5, No.4, 2019
76 | P a g e www.iiste.org
Reed, B.A., Grivetti, L.E. (2000). Controlling on-farm inventories of bulk-tank raw milk-An
opportunity to protect public health. J. Dairy Sci. 83(12): 2988-2991.
Riahi, E., Ramaswamy, H.S. (2004). High pressure inactivation kinetics of amylase in apple juice. J.
Food Eng. 64(2): 151-160.
SAS. (1999). SAS/STAT User’s Guide. Version 8, first edition, SAS Publishing. Cary. 1-2552.
Shi, J., Yu, J., Pohorly, J.E., Kakuda, Y. (2003). Polyphenolics in grape seeds-biochemistry and
functionality. J. Med. Food. 6(4): 291-299.
Shiraishi, M., Fujishima, H., Chijiwa, H. (2010). Evaluation of table grape genetic resources for sugar,
organic acid, and amino acid composition of berries. Euphytica. 174(1): 1-13.
Tasnim, F., Hossain, M.A., Nusrath, S., Hossain, M.K., Lopa, D., Haque, K.M. (2010). Quality
assessment of industrially processed fruit juices available in Dhaka city, Bangladesh. Malays. J.
Nutr. 16(3): 431-438.
Watts, B.M., Ylimaki, G.L., Jeffery, L.E. and Elias, L.G. (1989). Basic sensory methods for food
evaluation. IDRC, Ottawa, 1-164.
Wesche-Ebeling P., Montgomery M.W. (1990). Strawberry polyphenoloxidase: Extraction and partial
characterization. J. Food Sci. 55(5): 1320–1324.
Wisal, S., Ullah, J., Zeb, A., Khan, M.Z. (2013). Effect of refrigeration temperature, sugar
concentrations and different chemicals preservatives on the storage stability of strawberry
juice. Int. J. Eng. Technol. 13(02): 160-168.
Xu, K., Aide Wang, A., Brown, S. (2012). Genetic characterization of the Malocus with pH and
titratable acidity in apple. Mol. Breed. 30(2): 899-912.
Yemenicioğlu, A., Özkan, M. And Cemeroğlu, B. (1997). Heat inactivation kinetics of apple
polyphenoloxidase and activation of its latent form. J. Food Sci. 62(3): 508-510.
Zemel, G.P., Sims, C.A., Marshall, M.R., Balaban, M. (1990). Low pH inactivation of
polyphenoloxidase in apple juice. J. Food Sci. 55(2): 562-563.